June 2016 Paper 1 Q2
2 \(4\begin{pmatrix} 1 - 2a \\ a \end{pmatrix} = \begin{pmatrix} b \\ 12 \end{pmatrix}\)
Work out the values of \(a\) and \(b\). [3 marks]
| Answer | Mark | Comments |
|---|---|---|
| Alternative method 1 | ||
| \(a = 3\) | B1 | |
| \(4 - 8a = b\) or \(4(1 - 2a) = b\) | M1 | oe eg \(\ 4 \times 1 + -2a \times 4 = b\) |
| \(b = -20\) | A1ft | ft from B0 M1 |
| Alternative method 2 | ||
| \(a = 3\) | B1 | |
| \(\begin{pmatrix} 4 - 8a \\ 4a \end{pmatrix}\) | B1 | Condone no brackets but do not condone a fraction |
| \(b = -20\) | B1ft | ft from B0 B1 |
Additional guidance
alt 1 ... \(a = 12\) B0, \(b = -92\) M1 A1ft